The kingdom of Maes Gwyddno, more commonly known as Cantre’r Gwaelod, is said to lie under the Irish Sea in Cardigan Bay.
It was ruled by Gwyddno Garanhir (Longshanks), born circa 520AD.
The land was said to be extremely fertile but depended on a dyke to protect it from the sea. The dyke had sluice gates which were opened at low tide to drain the water from the land, and closed as the tide returned.
In around 600AD, a storm blew up from the south west, driving the spring tide against the sea walls. The appointed watchman, Seithennin, a heavy drinker and friend of the king, was at a party in the king’s palace near Aberystwyth.
Some say he fell asleep due to too much wine, or that he was too busy having fun, to notice the storm and to shut the gates.
The water gates were left open, and the sea rushed in to flood the land of the Cantref, drowning more than 16 villages.
Black Boy Inn, Northgate Street, Caernarfon, Gwynedd, LL55 1RW Tel 01286 673604